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DOCSIS

Does Docsis Have a 5-Gig Future?

DENVER -- Cable Next-Gen Broadband Strategies -- The cable industry has hardly scratched the multi-gigabit potential of Docsis, according to a Cisco Systems Inc. (Nasdaq: CSCO) exec.

Once MSOs get an opportunity to use their full slate of spectrum for IP, "we can see how to get to 5Gbit/s down and 1Gbit/s up," said John Chapman, CTO of Cisco's cable access business unit and a Cisco fellow, during his Tuesday keynote here.

He didn't say when that would happen, but it would be more than a quantum leap from where things stand today. Current-generation Docsis 3.0 gear can bond eight downstream channels and four upstream channels -- enough for more than 300Mbit/s down and 100Mbit/s up. Within a year, Chapman sees the advent of cable modem models that can bond 24 channels, giving cable the potential for 1Gbit/s downstream bursts.

"Docsis is just a teenager in many ways," Chapman said, noting that cable is utilizing just 1 percent to 2 percent of its spectrum with the bonding of eight downstream channels. He believes MSOs will need to allocate about 20 Docsis channels to support a full IP video migration. Some industry experts think cable will probably need more. (See MSOs Must Bust Out Bandwidth for IP Video Leap.)

(The other way in which Doscis is a teenager is literal: It's turning 15. The 1.0 specifications were issued March 26, 1997, represented by a mere 172 pages.)

Docsis is far from being a reliable conduit for video services, Chapman warned. Prepping Docsis for managed IP-video services -- as opposed to today's unmanaged over-the-top video -- represents "the next technical challenge for our community," he said.

Chapman also stressed that Docsis doesn't compete with the EPON Over Coax (EPoC) standard being developed by the Institute of Electrical and Electronics Engineers Inc. (IEEE) . They use the same cable spectrum, but Docsis is primarily used for residential data, while EPoC will likely target business-class services at first, he said. (See Why Cable Needs EPON Over Coax and EPON-Over-Coax Starts Its Standards Journey .)

— Jeff Baumgartner, Site Editor, Light Reading Cable



AESerm 12/5/2012 | 5:38:35 PM
re: Does Docsis Have a 5-Gig Future?

Near term, there's the question is how much of an IP migration 750 Mbps (20 bonded channels) could support. One MSO exec suggested looking at % of monthly Internet traffic consumed by Netflix and the time consumers spend using the service, then compare that with amount of video a cable sub views per month. Bill Niemeyer of TDG recently estimated NFLX viewing approaching 2% of VOD, with VOD representing 1% of all TV viewing. Last Sept Sandvine said NFLX was peaking at 32% of Internet traffic. Upshot seems to be that if these numbers are roughly correct, even upping D3 by 250% (to 750 Mbps) only takes care of a fraction of an entire lineup. But then I could be missing something here. 

fgoldstein 12/5/2012 | 5:38:32 PM
re: Does Docsis Have a 5-Gig Future?

750 Mbps is not enough to replace the linera channels per se.  But if there weren't too many homes/node, then a number of less-watched channels could be moved to SDV, and only put onto the pipe if someone were watching them.  Hey, ti (wort of) works for uVerse.


Moving linear video to a big fat download pipe makes a lot of sense, as the old channelized QAM format is a vestige of analog delivery, which is fading out.  But maybe it shouldn't just be an expansion of DOCSIS, which was designed for something else.  A new downstream paradigm, or at least PMD, might be appropriate.


 

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